H Advanced Concepts of CDMA SLIDE 1 Copyright Hewlett Packard © 1999 Advanced Training Version -...

Advanced Concepts of CDMA SLIDE 1 Copyright Hewlett Packard © 1999

Advanced Training Version - 6th Edition

Concepts of Concepts of CDMACDMA


Power

Frequency

Time

FDMA

Frequency

Power

Time

TDMA

Frequency

CDMA

Power

Time

Cellular Access Cellular Access MethodsMethods


US Cellular Channel 384

Frequency

Amplitude

Frequency

Amplitude

AMPS

45 MHz

Forward Link

881.52 MHz836.52 MHz

Reverse Link

CDMA

45 MHz

836.52 MHz 881.52 MHz

Reverse Link Forward Link

CDMA is Also Full CDMA is Also Full DuplexDuplex


3

6

CDMA Reuse FDMA Reuse

11

1

1

11

11

16

22

1

45

7

Cellular Frequency Cellular Frequency Reuse PatternsReuse Patterns


Capacity =

(Chan BW)(Data Rate)

× (1)(S/N)

× (1)(Vaf)

(Fr)×

CDMA = (1,230,000)(9,600)

× (1)(5.01)

× (1)(.40)

(0.67)×

CDMA = 42 calls (Using 1.5 MHz BW)

AMPS = 1.5 MHz ÷ 30 kHz = 50 ChannelsCapacity = 50 Channels ÷ 7 (1/7 Frequency

Reuse)AMPS = 7 calls (Using 1.5 MHz BW)

Processing

Gain

Processing

Gain

CDMA Capacity GainsCDMA Capacity Gains


Interference Sources

Walsh CodeSpreading

Encoding &Interleaving

Decode & De-Interleaving

BasebandData

BasebandData

Background Noise

External Interference Other Cell InterferenceOther User Noise

9.6 kbps 19.2 kbps 1228.8 kbps 19.2 kbps 9.6 kbps

CDMA Transmitter

CDMA Receiver

1.23 MHz BW

fc

1.23 MHz BW

fc

10 kHz BW

0

10 kHz BW

0

1.23 MHz BW

fc

1.23 MHz BW

fcfc

-113 dBm/1.23 MHz

fc

Spurious Signals

Walsh CodeCorrelator

1228.8 kbps

The CDMA ConceptThe CDMA Concept


Received Signal

Time

Correlation = 1

Correlation = 0

Correlation = 0

Correlation = 0

What is Correlation ?What is Correlation ?

• Is a Measure of How Well a Given Signal Matches a Desired Code

• The Desired Code is Compared to the Given Signal at Various Test Times


CDMA

CDMA

Analog

Analog

CDMA Paradigm ShiftCDMA Paradigm Shift

• Multiple Users on One Frequency– Analog/TDMA Try to Prevent

Multiple Users Interference

• Channel is Defined by Code– Analog Systems Defined

Channels by Frequency

• Capacity Limit is SoftAllows Degrading Voice Quality to

Temporarily Increase CapacityReduce Surrounding Cell Capacity to

Increase a Cell's Capacity


CDMA DiversityCDMA Diversity

• Spatial Diversity– Making Use of Differences in Position

• Frequency Diversity– Making Use of Differences in Frequency

• Time Diversity– Making Use of Differences in Time


CDMA Spatial CDMA Spatial DiversityDiversity

• Diversity Reception:– Multiple Antennas at Base Station

Each Antenna Is Affected by Multipath Differently Due to Their Different Location

Allows Selection of the Signal Least Affected by Multipath Fading

• If Diversity Antennas Are Good, Why Not Use Base Stations as a Diversity Network?– Soft Handoff


MTSO

Vocoder / Selector

Base Station 2Base Station 1

Land Link

Spatial Diversity Spatial Diversity During Soft HandoffDuring Soft Handoff


Amplitude

Frequency

1.23 MHz BW

CDMA Frequency CDMA Frequency DiversityDiversity

• Combats Fading, Caused by Multipath• Fading Acts like Notch Filter to a Wide

Spectrum Signal• May Notch only Part of Signal


CDMA Time DiversityCDMA Time Diversity

• Rake Receiver to Find and Demodulate Multipath Signals

• Data is Interleaved– Spreads Adjacent Data in Time to

Improve Error Correction Efficiency

• Convolutional Encoding– Adds Error Correction and Detection

• Viterbi Decoding– Most Likely Path Decoder for

Convolutionaly Encoded Data


Original Data Original Data FrameFrame

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Errors/Time

Interleaved Data FrameInterleaved Data Frame

Errors/Time1 5 9 13 2 6 10 14 3 7 11 15 4 8 12 16

Errors/Time

TX

RX

1 2 3 4 5 6 7 8 9 10 11 12 13 15 1614

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Errors/Time

TX

RX

1 2 3 45 6 7 89 10 11 1213 14 15 16

1 5 9 132 6 10 143 7 11 154 8 12 16

1 2 3 45 6 7 89 10 11 1213 14 15 16

Why Interleaving Why Interleaving WorksWorks


Time

Frequency

Amplitude

The Rake ReceiverThe Rake Receiver


Output

T0

W0

T4T1 T2 T3

W1 W2 W3 W4

+

Delay Taps

Tap Weights

Antenna

Rake Receiver DesignRake Receiver Design


SynchronizationSynchronization

• All Direct Sequence, Spread Spectrum Systems Should be Accurately Synchronized for Efficient Searching

• Finding the Desired Code Becomes Difficult Without Synchronization


Reverse Link Power Reverse Link Power ControlControl

• Maximum System Capacity is Achieved if:All Mobiles are Powered Controlled to the Minimum

Power for Acceptable Signal QualityAs a result, all Mobiles are Received at About Equal

Power at the Base Station Independent of Their Location

• There are Two Types of Reverse Control:– Open Loop Power Control– Closed Loop Power Control

• Open & Closed Loop Power Control are Always Both Active !


Open Loop Power Open Loop Power ControlControl

• Assumes Loss is Similar on Forward and Reverse Paths

• Receive Power+Transmit Power = -73– All powers in dBm

• Example:– For a Received Power of -85 dBm

Transmit Power = (-73) - (-85) Transmit Power = +12 dBm

• Provides an Estimate of Reverse TX Power for Given Propagation Conditions


Closed Loop Power Closed Loop Power ControlControl

• Directed by Base Station• Updated Every 1.25 msec• Commands Mobile to Change TX

Power in +/-1 dB Step Size• Fine Tunes Open Loop Power Estimate• Power Control Bits are "Punctured"

over the Encoded Voice Data• Puncture Period is two 19.2 kbps

Symbol Periods = 103.6 usec


CDMA Variable Rate CDMA Variable Rate Speech CoderSpeech Coder

• DSP Analyzes 20 Millisecond Blocks of Speech for Activity

• Selects Encoding Rate Based On Activity:High Activity: Full Data Rate Encoding (9600 bps)Some Activity: Half Data Rate Encoding (4800 bps)Low Activity: Quarter Date Rate Encoding (2400

bps)No Activity: 1/8 Data Rate Encoding (1200 bps)

• How Does This Improve Capacity? – Mobile Transmits in Bursts of 1.25 ms

• System Capacity Increases by 1/Vaf


CDMA Frame = 20 ms

Full Rate

Half Rate

Quarter Rate

Eighth Rate

Mobile Power BurstingMobile Power Bursting

• Each Frame is Divided Into 16 Power Control Groups

• Each Power Control Group Contains 1536 Chips (represents 12 encoded voice bits)

• Average Power Is Lowered 3dB for Each Lower Data Rate


Base Station Variable Base Station Variable Rate VocoderRate Vocoder

• Base Stations Do Not Pulse TX Channels

• How Does the Base Station Handle Variable Rate Vocoding ?– Repeats Data Bits When Transmitting at

Reduced Rates– Repeating Data Adds 3 dB Coding Gain– Lowers the TX Power 3 dB for Each Lower

Rate


WalshCover

I Short Code

Q Short Code

FIR

FIR1.2288Mbps

Walsh Code Generator

I

Q

1.2288Mbps

1.2288 Mbps

1.2288 Mbps

Long Code

19.2 kbps

19.2 kbps

Vocoded Speech data

20 msec blocks

Interleaver

Power Control

Puncturing

19.2 kbps

19.2 kbps

800 bps

800 bps

P.C.MUX

9.6 kbp

s

19.2 kbps

3/4 rate

1/2 rate

14.4 kbp

s

19.2 kbps

Convolutional

Encoder Long CodeScramblin

g

Short Code Scrambler

Forward Link Traffic Forward Link Traffic Channel Physical Channel Physical LayerLayer


CDMA VocodersCDMA Vocoders

• Vocoders Convert Voice to/from Analog Using Data Compression

• There are Three CDMA Vocoders:– IS-96A Variable Rate (8 kbps maximum)– CDG Variable Rate (13 kbps maximum)– EVRC Variable Rate (improved 8 kbps)

• Each Has Different Voice Quality:IS-96A - moderate qualityEVRC - near toll qualityCDG - toll quality


12 8171

192 bits in a 20 ms Frame

Information Bits

CRCEncoder Tail Bits

9600 bpsFrame

879


Information Bits

4800 bpsFrame

8

839


Information Bits

Encoder Tail Bits

2400 bpsFrame

815


Information Bits

Encoder Tail Bits

1200 bpsFrame


12 8266


Information Bits


8124


Information Bits

10

854


Information Bits

820


Information Bits

14400 bpsFrame

7200 bpsFrame

3600 bpsFrame

1800 bpsFrame


8


6


1-bit Reserved or Frame Erasure

Mixed Mode

bit

Mixed Mode

bit

Mixed Mode

bit

Mixed Mode

bit

Mixed Mode bit

Mixed Mode bit

Mixed Mode bit

Mixed Mode bit

CDMA Frame FormatsCDMA Frame Formats





+Data In9600 bps

Data Out9600 bps

Data Out9600 bps

D D DD D DD D

+

Forward Error Forward Error ProtectionProtection

• Uses Half-Rate Convolutional Encoder• Outputs Two Bits of Encoded Data for

Every Input Bit


ConvolutionalEncoder

14.4 kbps

19.2 kbps

Vocoded Speech data

3/4 rate

20 msec blocks

14.4 14.4 TCH Forward Link TCH Forward Link ModificationsModifications

• Replaces 8 kbps Vocoder with a 13 kbps Vocoder (both Variable Rate)

• Effects:Provides Toll Quality SpeechUses a 3/4 Rate EncoderReduces Processing Gain

1.76 dBResults in Reduced Capacity

or Smaller Cell Sizes


112

2

3

4567

89

1011

CDMA System TimeCDMA System Time

• How Does CDMA Achieve Synchronization for Efficient Searching ?

Use GPS Satellite System

• Base Stations Use GPS Time via Satellite Receivers as a Common Time Reference

• GPS Clock Drives the Long Code Generator


Modulo-2 Addition

Long Code Output

34 12

User AssignedLong Code Mask

42 bits

4142 55

Long Code Generator

Long Code GenerationLong Code Generation


Long CodeGenerator

EncodedVoice Data

19.2 kbps

1.2288 Mbps

XOR

Long CodeDecimator

19.2 kbps

19.2 kbps

Long Code ScramblingLong Code Scrambling

– User's Long Code Mask is Applied to the Long Code

– Masked Long Code is Decimated Down to 19.2 kbps

– Decimated Long Code is XOR'ed with Voice Data Bits

– Scrambles the Data to Provide Voice Security


Long CodeDecimatedData

Long Code Scrambled Voice Data

19.2 kbps

Long CodeDecimator

19.2 kbps

19.2 kbps

800 bps

P.C.Mux

Closed Loop Power Control Bits

800 bps

Closed Loop Power Closed Loop Power Control PuncturingControl Puncturing– Long Code is

Decimated Down to 800 bps

– Decimated Long Code Controls the Puncture Location

– Power Control Bits Replace Voice Data

– Voice Data is Recovered by the Mobile's Viterbi Decoder


W =2

0 00 1

4W =

0 0 0 00 1 0 10 0 1 10 1 1 0

W = 01

n

n

n

n

W WW WW =

2n

Walsh CodesWalsh Codes


Cross Correlation

N agreements - N disagreementsN

total_number_of_digits

=

W =

0 0 0 00 1 0 10 0 1 10 1 1 0

4

0 0 0 00 0 1 1Y Y N N

2 match - 2 don't =0

Checking for Checking for OrthogonalityOrthogonality


What is theSpreading RateIncrease ?

EncodedVoice Data

19.2 kbps

1.2288 Mbps

1.2288 Mbps

XOR

Walsh CodeGenerator

Walsh Code SpreadingWalsh Code Spreading


To I/QModulator

1.2288 Mbps

1.2288 Mbps

Q Channel ShortSequence CodeGenerator

Walsh CodedData at1.2288 Mbps

I Channel ShortSequence CodeGenerator

Why Spread Again Why Spread Again with the Short with the Short Sequence ?Sequence ?– Provides a Cover to

Hide the 64 Walsh Codes

– Each Base Station is Assigned A Time Offset in its Short Sequences

– Time Offsets Allow Mobiles to Distinguish Between Adjacent Cells

– Also Allows Reuse of All Walsh Codes in Each Cell


chip

0 5 10 15 20 25 30

1

Pseudo-Random Sequence

0

-1

chip offset

Auto-Correlation Versus Time Offset

0 5 10 15 20 25 30

0

Auto-CorrelationAuto-Correlation

• Is a Comparison of a Signal Against Itself

• Good Pseudo-Random Patterns Have:

Strong Correlation at Zero Time Offset

Weak Correlation at Other Time Offsets


chip offset

Auto-Correlation VersusTime Offset with 17 dB Noise

Added

0 5 10 15 20 25 30

0

Short Code CorrelationShort Code Correlation

– Short Codes Are Designed to Have:Strong Auto-Correlation

at Zero Time OffsetWeak Auto-Correlation

at Other OffsetsGood Auto-Correlation

In Very Poor Signal-to -Noise Ratio Environments

– Allows Fast Acquisition in Real World Environment


Walsh Code 32

Walsh Code 0

Pilot Channel

Sync Channel

Walsh Codes 1 to 7

Walsh Codes 8-31, 33-63

Traffic Channels1 up to 55 Channels

All 0's

19.2 kbps 1228.8 kbps

1228.8 kbps

1228.8 kbps

I

Convert to I/Q & Short Code Spreading



FIR LP Filter &D/A Conversion




Q

4.8 kbps

I Data

I Data

I Data

I Data

Q Data

Q Data

Q Data

Q Data

Paging Channels1 up to 7 Channels

19.2 kbps 1228.8 kbps Convert to I/Q & Short Code Spreading

Forward Link Channel Forward Link Channel FormatFormat


+Sum of A & BWalsh EncodedData Streams

W =20 00 1

- User A- User B

For a 0 Input,Use Code 00

Channel AVoice Data

+10

0 0 01

Channel AWalsh EncodedVoice Data

-1

+1

1 100 0 0 0 0

For a 1 Input,Use Code 11-1

+1

1 1

-1

+1

0 0

User A For a 0

Input,Use Code 01-1

+1

For a 1 Input,use code 10-1

+1

Channel BVoice DataChannel BWalsh EncodedVoice Data

+10 1 10 0

-1

+1

1 10 0 00 1 1

1

User B

10

0

-1

+2

+1

-2

Walsh Coding ExampleWalsh Coding Example


Original User A Voice Data+10

0 0 01

Multiply Summed Data with Desired Walsh Code

+10 1 10 0

-1

+1

1 0

+2

-1

+1

-2

User A + B Walsh Data

+2

Correlation Coefficient

-1

+1

1 1-1

+1

-2

x =

+2

-1

+1

-2

+2

-1

+1

-2

Original User B Voice Data

-1

+1

-2

+2

-1

+1

-2

= 1+2Multiply Summed Data with Desired Walsh Code

User A + B Walsh Data1

T0

T

z =ij

fi (t) f (t)j dt

= =x1-

Walsh Decoding Walsh Decoding ExampleExample


+Sum of A & BWalsh EncodedData Streams

Channel AWalsh EncodedVoice Data

-1

+1

1 100 0 0 0 0

Channel BWalsh EncodedVoice Data

-1

+1

1 10 0 00 1 1

-1

+2

+1

-2

Multiply Summed Data with Desired Walsh Code+2

-1

+1

1 1-1

+1

-2

x =

+2

-1

+1

-2

= 0.75-Original Data Was0 (-1), We Have Interference Now!

Original Time Delayed

What if Walsh Codes What if Walsh Codes are Not Time Aligned ?are Not Time Aligned ?


Uses Walsh Code 0:All 64 bits are 0

All Data into Walsh Modulator is 0

Output of Walsh Modulator is Therefore all 0's

Pilot Channel is just the Short Codes

Q

Walsh Code

0

I Short Code

Q Short Code

FIR

FIR1.2288Mbps


I

1.2288Mbps

1.2288 Mbps

1.2288 Mbps

All 0 inpu

t


WalshModulato

r

Pilot Channel Physical Pilot Channel Physical LayerLayer


Walsh32

Cover

I Short Code

Q Short Code

FIR

FIR1.2288Mbps


I

Q

1.2288Mbps

1.2288 Mbps

1.2288 Mbps

Sync Channel Message Data

Interleaver

4.8 kbp

s

1/2 rate

Convolutional

Encoder


2x

4.8 kbp

s

SymbolRepetition

2.4 kbp

s

1.2 kbp

s

Sync Channel Physical Sync Channel Physical LayerLayer


Walsh

1 to 7Cover

I Short Code

Q Short Code

FIR

FIR1.2288Mbps


I

Q

1.2288Mbps

1.2288 Mbps

1.2288 Mbps

19.2 kbps

Paging Channel

Long Code

19.2 kbps

Long CodeScramblin

g


Paging Channel Message Data

Interleaver

19.2 kbp

s

1/2 rate

Convolutional

Encoder

2x

19.2 kbp

s

SymbolRepetition

9.6 kbp

s

4.8 kbp

s

Paging Channel Paging Channel Physical LayerPhysical Layer


Interleaver

I Short Code

Q Short Code

1.2288Mbps

I

Q

307.2 kbps

t/2

1/2 Chip Delay28.8 kbps

20 msec blocks

Vocoded Speech Data

64-ary Modulator

1.2288 Mbps

1 of 64 Walsh Codes

Long Code

1.2288 Mbps

1.2288 Mbps

FIR

FIR

Walsh Code 1

Walsh Code 2

Walsh Code 0

Walsh Code 62

Walsh Code 63

Walsh Code 61

Convolutional

Encoder

9.6 kbps

28.8 kbps

1/3 rate

1/2 rate

14.4 kbps

28.8 kbps

Long Code Modulator


Reverse Link Traffic Reverse Link Traffic Channel Physical Channel Physical LayerLayer


Data In9600 bps

Data Out9600 bps

Data Out9600 bps

+D D DD D DD D

++ Data

Out9600 bps

Reverse Error Reverse Error ProtectionProtection

• Uses Third-Rate Convolutional Encoder

• Outputs Three Bits for Every Input Bit


ConvolutionalEncoder

14.4 kbps

28.8 kbps

Vocoded Speech data

1/2 rate

20 msec blocks

14.4 14.4 TCH Reverse Link TCH Reverse Link ModificationsModifications

• Replaces 8 kbps Vocoder with a 13 kbps Vocoder (both Variable Rate)

• Effects:Provides Toll Quality SpeechUses a 1/2 Rate EncoderReduces Processing Gain 1.76

dBResults in Reduced Capacity

or Smaller Cell Sizes


307.2 kbps

Walsh Code 1

Walsh Code 2

Walsh Code 0

Walsh Code 62

Walsh Code 63

Walsh Code 61

28.8 kbps

64-64-ary Modulationary Modulation

• Every 6 Encoded Voice Data Bits Points to One of the 64 Walsh Codes

• Spreads Data From 28.8 kbps to 307.2 kbps:

(28.8 kbps * 64 bits)/ 6 bits = 307.2 kbps)

• Is Not the Channelization for the Reverse Link


Why Aren't Walsh Codes Why Aren't Walsh Codes Used for Reverse Used for Reverse Channelization ?Channelization ?• All Walsh Codes Arrive Together in Time to All Mobiles From the Base Station

• However, Transmissions from Mobiles DO NOT Arrive at the Same Time at the Base Station


WalshModulatedVoice Data

307.2 kbps

1.2288 Mbps

1.2288 Mbps

XOR

Long CodeGenerator

Reverse Channel Long Reverse Channel Long Code SpreadingCode Spreading

• Long Code Spreading Provides Unique Mobile Channelization

• Mobiles are Uncorrelated but not Orthogonal with Each Other


t/2 QFIR

I Short Code

Q Short Code

1.2288Mbps

I

1/2 Chip Delay

1.2288 Mbps

1.2288 Mbps

FIR

Reverse Channel Short Reverse Channel Short Sequence SpreadingSequence Spreading

• Same PN Short Codes Are Used by Mobiles

• Short Sequence Spreading Aids Base Station Signal Acquisition

• Extra 1/2 Chip Delay is Inserted into Q Path to Produce OQPSK Modulation to Simplify Power Amplifier Design


I

Q

I

Q

00 01

11

01

1110

00

10

OQPSK ModulationOQPSK Modulation

• QPSK Makes one Symbol Change Every Period

• OQPSK Makes two Symbol Changes Every Period if both I and Q Data Changes

• Example Symbol Pattern is:– 00, 10, 01,11


Filtered Offset QPSK

Filtered QPSK

I I

QQ

Base Station Pilot Channel TX Mobile Station TX

CDMA Modulation CDMA Modulation FormatsFormats


Function Forward Link{Base to Mobile}

Reverse Link{Mobile to Base}

9.6 kbps Convolutional

Encoder

1/2 Rate{9600 in 19200 out}

1/3 Rate{9600 in 28800 out}

14.4 kbps Convolutional

Encoder

3/4 Rate{14400 in 19200

out}

1/2 Rate{14400 in 28800

out}

Walsh Coding Channelization

64-ary Modulation

Long CodeSpreading

Voice Privacy Channelization

Short Code Spreading

Base Station Identification

Aid Base Station

Searching

Channelization Channelization SummarySummary


Forward Link{Base to Mobile}

Reverse Link{Mobile to Base}

+ -High Power Transmitter-Pilot Channel-Added Time Diversity-Orthogonal Code

Channels

-Wide Range Power Control-Diversity Reception at

Base

- -Complexity of Soft Handoff

-Non-coherent Demodulation

-Limited Power-Uncorrelated Code

Channels

Link Advantages & Link Advantages & DisadvantagesDisadvantages


Layer 2

Multiplex Sublayer

Layer 1Physical Layer

Channel Data - 9600 bps or 14400 bps

Traffic Channel

Primary TrafficLayer 2

SignalingLayer 2Link Layer

Paging & Access Channels

Layer 3Call Processing and

Control

CDMA Multiplex CDMA Multiplex SublayerSublayer


CDMA Service OptionsCDMA Service Options

• Service Options Are:1- Voice Using 9600 bps IS-96-A Vocoder2- Rate Set 1 Loopback (9600 bps)3- Voice Using 9600 bps (EVRC)4- Asynchronous Data Service (circuit switched)5- Group 3 Fax6- Short Message Service (9600 bps)7- Internet Standard PPP Packet Data 8- CDPD Over PPP Packet Data9- Rate Set 2 Loopback (14400 bps)14-Short Message Service (14400 bps)32,768- Voice Using 14400 bps (CDG)


EIA/TIA 95-BCombines TSB-74 & J-STD-008 for a Universal Protocol

J-STD-008Not Backwards Compatible, PCS only Protocol

IS-95 Rev ABackwards Compatible with IS-95. First Deployed Protocol

IS-95 Rev 0Original System- never actually deployed.

TSB-74Cellular Protocol that adds 14400 Channel Support ARIB T53

Japan CDMASystem Cellular

Protocol

CDMA Protocol StacksCDMA Protocol Stacks


Ten Minutes in the Ten Minutes in the Life of a CDMA Mobile Life of a CDMA Mobile PhonePhone• Turn-on

– System Access

• Travel– Idle State Hand-Off

• Initiate Call• System Access• Continue Travel

– Initiate Soft Handoff

– Terminate Soft Handoff

• End Call


CDMA Turn On ProcessCDMA Turn On Process

• Find All Receivable Pilot Signals– Choose Strongest One

• Establish Frequency and PN Time Reference (Base Station I.D.)

• Demodulate Sync Channel• Establish System Time• Determine Paging Channel Long

Code Mask


SYNCSYNC

Sync Channel MessageSync Channel Message

• Contains the Following Data:Base Station Protocol RevisionMin Protocol Revision SupportedSID, NID of Cellular SystemPilot PN Offset of Base StationLong Code StateSystem TimeLeap Seconds From Start of System TimeLocal Time Offset from System Time Daylight Savings Time FlagPaging Channel Data RateChannel Number


PagingPaging

Read the Paging Read the Paging ChannelChannel

• Demodulate the Paging Channel:

Use Long Code Mask Derived from the Pilot PN Offset Given in Sync Channel Message

• Decode Messages• Register, if Required by

Base Station• Monitor Paging Channel


–Overhead MessagesSystem Parameters Access ParametersCDMA Channel ListExtended System ParamsExtended Neighbor List

–Other MessagesOrderChannel AssignmentData Burst

–More MessagesAuthenticationSSD UpdateFeature NotificationStatus RequestService RedirectionGeneral PageGlobal Service RedirectionTMSI Assignment

J-STD-008 Paging Messages:

Paging Channel Paging Channel MessagesMessages


CDMA Idle State CDMA Idle State HandoffHandoff

• No Call In Progress• Mobile Listens to New Cell• Move Registration Location if Entering

a New Zone


CDMA Call InitiationCDMA Call Initiation

• Dial Numbers, Then Press Send• Mobile Transmits on a Special

Channel Called the Access Channel• The Access Probe Uses a Long

Code Mask Based On:Access & Paging Channel NumbersBase Station IDPilot PN Offset


Interleaver

I Short Code

Q Short Code

1.2288Mbps

I

Q

307.2 kbps

t/2

1/2 Chip Delay28.8 kbps

64-ary Modulator

1.2288 Mbps

1 of 64 Walsh Codes

Access Channel Long Code

1.2288 Mbps

1.2288 Mbps

FIR

FIR

Walsh Code 1

Walsh Code 2

Walsh Code 0

Walsh Code 62

Walsh Code 63

Walsh Code 61

Long Code Modulator


Access Channel Message Data

Convolutional

Encoder

2x

28.8 kbp

s

SymbolRepetition

14.4 kbp

s4.8 kbp

s

1/3 rate

Reverse Link Access Reverse Link Access Channel Physical Channel Physical LayerLayer


CDMA Call CompletionCDMA Call Completion

• Base Answers Access Probe using the Channel Assignment Message

• Mobile Goes to A Traffic Channel Based on the Channel Assignment Message Information

• Base Station Begins to Transmit and Receive Traffic Channel


CDMA Soft Handoff CDMA Soft Handoff InitiationInitiation

• Mobile Finds Second Pilot of Sufficient Power (exceeds T_add Threshold)

• Mobile Sends Pilot Strength Message to First Base Station

• Base Station Notifies MTSO• MTSO Requests New Walsh

Assignment from Second Base Station• If Available, New Walsh Channel Info

is Relayed to First Base Station


CDMA Soft Handoff CDMA Soft Handoff CompletionCompletion

• First Base Station Orders Soft Handoff with new Walsh Assignment

• MTSO Sends Land Link to Second Base Station

• Mobile Receives Power from Two Base Stations

• MTSO Chooses Better Quality Frame Every 20 Milliseconds


Ending CDMA Soft Ending CDMA Soft HandoffHandoff

• First BS Pilot Power Goes Low at Mobile Station (drops below T_drop)

• Mobile Sends Pilot Strength Message• First Base Station Stops Transmitting

and Frees up Channel• Traffic Channel Continues on Base

Station Two


CDMA End of CallCDMA End of Call

• Mobile or Land Initiated• Mobile and Base Stop Transmission• Land Connection Broken


CDMA

CDMA ConclusionsCDMA Conclusions

• New Access Method– Code Based

• Designed for Use in Interfering Environment

• Uses Multipath to Improve Reception in Fading Conditions

• Has High Capacity– 6 Times Analog for 14.4 kbps Voice– 10 Times Analog for 9.6 kbps Voice

H Advanced Concepts of CDMA SLIDE 1 Copyright Hewlett Packard © 1999 Advanced Training Version -...

Documents

Transcript of H Advanced Concepts of CDMA SLIDE 1 Copyright Hewlett Packard © 1999 Advanced Training Version -...